Equipment used to clean upholstery, carpets, and other structures which can keep and hold dirt need to be powerful in order to perform effectively. Cleaning solution, which may be a mixture of soap, water, or other cleaning agent should be applied hot, and removed quickly from the surface to be cleaned. Thus the means for removing the dirt laden cleaning solution should also be powerful and minimize the time in which the dirt laden cleaning solution is present, and maximize the efficiency with which it is removed.
The requirement for power carries an associated requirement of durability. Powerful cleaning machines require durable working parts to form a machine having long life and low maintenance. However, the cost of such machinery, given the requirements for power and durability, tend to rise significantly if not designed with an efficiency of cost in mind.
The severity of service should also be taken to account. The environment in which an extractor works has tendencies toward corrosion and the associated structural weakening problems caused by such corrosion. Thus the structures used should not only be corrosion resistant, but should also be accessible for cleaning of the unit since cleaning minimizes the long term effects of exposure to cleaning solution. Cleanability is also important for appearance, and operation of a cleaning unit in areas which are easily soiled by transportation of the cleaning unit.
In addition, the unit should be designed with the operating environment in mind. The exterior of the unit should be free from sharp edges which might damage the walls of its surroundings during its use. The needed unit should, even if inadvertently brushed against a wall, create minimal damage.